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Abstract:

A storage system having a plurality of storage devices including a first
type storage device and a second type storage device, a reliability
attribute and/or a performance attribute of the first type storage device
being different from a reliability attribute and/or a performance
attribute of the second type storage device. The storage system also has
a control unit and managing a plurality of virtual volumes. If necessary,
a storage area allocated to a first portion of a virtual volume of the
plurality of virtual volumes is changed from a first type storage area of
the plurality of first type storage areas to a second type storage area
of the plurality of second type storage areas while another first type
storage area of the plurality of first type storage areas is allocated to
a second portion of the virtual volume.

Claims:

1. A storage system comprising: a plurality of storage devices including
first type storage devices and second type storage devices, the second
type storage devices having a different reliability and/or performance
attribute from the first type storage devices; and a control unit
configured to manage a virtual volume including a first portion to which
a first storage area provided by the first type storage devices is
allocated, the virtual volume being a copy destination of a source
volume, wherein the control unit is configured to allocate a second
storage area provided by the second type storage devices to the first
portion of the virtual volume, instead of the first storage area, by
considering an access frequency of a first portion of the source volume
which corresponds to the first portion of the virtual volume.

2. The storage system according to claim 1, wherein the control unit is
configured to manage the source volume.

3. The storage system according to claim 1, wherein the storage system is
coupled to another storage system which is configured to provide the
source volume.

4. The storage system according to claim 1, wherein the first portion of
the virtual volume and the first portion of the source volume are in a
relation of a copy pair.

5. The storage system according to claim 1, wherein the virtual volume is
defined by a plurality of same-sized chunks, to each of which one of the
plurality of storage area is allocated.

6. The storage system according to claim 1, wherein the control unit is
configured to manage a second portion, of the virtual volume, to which a
third storage area provided by the second type storage devices is
allocated, the second portion of the virtual volume corresponding to a
second portion of the source volume, and upon occurrence of a failure in
the source volume, the controller is configured to change the allocation
of the second portion of the virtual volume from the third storage area
provided by the second type storage devices to a fourth storage area
provided by the first type storage devices.

7. In a storage system having a control unit and a plurality of storage
devices including first type storage devices and second type storage
devices, the second type storage devices having a different reliability
and/or performance attribute from the first type storage devices, a
method comprising the steps of: managing, by the control unit, a virtual
volume including a first portion to which a first storage area provided
by the first type storage devices is allocated, the virtual volume being
a copy destination of a source volume; and allocating, by the control
unit, a second storage area provided by the second type storage devices
to the first portion of the virtual volume, instead of the first storage
area, by considering an access frequency of a first portion of the source
volume which corresponds to the first portion of the virtual volume.

8. The method according to claim 7, further comprising the step of:
managing, by the control unit, the source volume.

9. The method according to claim 7, wherein the storage system is coupled
to another storage system which is configured to provide the source
volume.

10. The method according to claim 7, wherein the first portion of the
virtual volume and the first portion of the source volume are in a
relation of a copy pair.

11. The method according to claim 7, wherein the virtual volume is
defined by a plurality of same-sized chunks, to each of which one of the
plurality of storage area is allocated.

12. The method according to claim 7, further comprising the steps of:
managing, by the control unit, a second portion, of the virtual volume,
to which a third storage area provided by the second type storage devices
is allocated, the second portion of the virtual volume corresponding to a
second portion of the source volume; and upon occurrence of a failure in
the source volume, changing, by the control unit, the allocation of the
second portion of the virtual volume from the third storage area provided
by the second type storage devices to a fourth storage area provided by
the first type storage devices.

13. A non-transitory computer readable storage medium operable in a
storage system having a control unit and a plurality of storage devices
including first type storage devices and second type storage devices, the
second type storage devices having a different reliability and/or
performance attribute from the first type storage devices, the
non-transitory computer readable storage medium storing thereon a program
comprising: code for managing a virtual volume including a first portion
to which a first storage area provided by the first type storage devices
is allocated, the virtual volume being a copy destination of a source
volume; and code for allocating a second storage area provided by the
second type storage devices to the first portion of the virtual volume,
instead of the first storage area, by considering an access frequency of
a first portion of the source volume which corresponds to the first
portion of the virtual volume.

14. The non-transitory computer readable storage medium according to
claim 13, further comprising: code for managing the source volume.

15. The non-transitory computer readable medium according to claim 13,
wherein the storage system is coupled to another storage system which is
configured to provide the source volume.

16. The non-transitory computer readable medium according to claim 13,
wherein the first portion of the virtual volume and the first portion of
the source volume are in a relation of a copy pair.

17. The non-transitory computer readable medium according to claim 13,
wherein the virtual volume is defined by a plurality of same-sized
chunks, to each of which one of the plurality of storage area is
allocated.

18. The non-transitory computer readable medium according to claim 13,
further comprising: code for managing a second portion, of the virtual
volume, to which a third storage area provided by the second type storage
devices is allocated, the second portion of the virtual volume
corresponding to a second portion of the source volume; and code for,
upon occurrence of a failure in the source volume, changing the
allocation of the second portion of the virtual volume from the third
storage area provided by the second type storage devices to a fourth
storage area provided by the first type storage devices.

Description:

CROSS-REFERENCE TO PRIOR APPLICATION

[0001] This is a continuation application of U.S. application Ser. No.
13/165,025, filed Jun. 21, 2011, which is a continuation application of
U.S. application Ser. No. 12/862,103, filed Aug. 24, 2010, which is a
continuation of U.S. application Ser. No. 12/194,638, filed Aug. 20, 2008
(now U.S. Pat. No. 7,801,933), which is a continuation of U.S.
application Ser. No. 11/328,103, filed Jan. 10, 2006 (now U.S. Pat. No.
7,430,572), which is a continuation of U.S. application Ser. No.
10/880,503, filed Jul. 1, 2004 (now U.S. Pat. No. 7,035,883). This
application relates to and claims priority from Japanese Patent
Application No. 2004-116069, filed on Apr. 9, 2004. The entirety of the
contents and subject matter of all of the above is incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a storage control system and
method for controlling the storage of data to the storage device.

[0004] 2. Description of the Related Art

[0005] In a system handling large amount of data, such as database system
in a data center, data is managed using a storage control system that is
built separately from the host computer. This storage control system is a
disk array system, such as a RAID Redundant Array of
Independent/Inexpensive Disks), where many storage devices are enclosed
in an array.

[0006] In such a storage control system, backup for copying data recorded
in the storage device to another storage device is performed so that the
data can be recovered even if the data recorded in the storage device
become damaged. In this case, consistency of data must be guaranteed
during the copying operation, because if the copied data is updated
during the copying operation, a mismatch of data occurs, and the backup
becomes meaningless.

[0007] A method for guaranteeing consistency of the backup data is to stop
the program, besides the backup program, that access the data. But in
case of a system for which high availability is required, programs cannot
be stopped for a long time. Therefore it is necessary to provide a system
that creates a stored image of the data at the point of the start of
backup without interrupting the programs from updating data during
backup. Hereafter the stored image of the data at a certain point in time
is called "volume copy", and the method which allows the system to update
the data while having the volume copy of a specified point in time is
called "volume copy management method". Creating of a volume copy is
called "volume copy acquisition", and the data which is the target of
volume copy acquisition is called "original data". Stopping the status
where the volume copy exists is called "volume copy deletion".

[0008] One of the volume copy management methods is by duplicating data.

[0009] According to this method, for example, from a normal state where a
volume copy is not acquired, a program on the storage control system
creates all data on two storage areas (that is, data is duplicated). And
the storage control system separates the two storage areas into
individual storage areas, provides data existing on one storage area as
original data, and provides the data existing on the other storage area
as volume copy.

[0010] While the volume copy is acquired and duplication is being stopped
(non-mirroring state), the storage control system enables update for the
storage area of original data, and records the location of data update if
a data update is generated. In the case of volume copy deletion, the
storage control system restarts the duplication of the data, and copies
the update data, of which content does not match between the two storage
areas, from the storage area of the original data to the storage area
provided as volume copy. This copying is called "mirror
resynchronization". In the case of volume copy deletion, the update data
may be copied from the storage area of the volume copy to the storage
area of the original data, which is the opposite of the above procedure,
and such copying is called "reverse mirror resynchronization".

[0011] The method of duplicating data by a program on a computer is shown
in U.S. Pat. No. 5,051,887, for example.

[0012] As the storage device, a disk device (e.g. hard disk drive),
magnetic tape storage device, or any other form of physical storage
device can be used. Disk devices include high reliability high
performance disk devices which are expensive but which have high
reliability and performance, and low reliability low performance disk
devices which are inexpensive but which have a lower reliability and
performance than high reliability high performance disk devices. An
example of a high reliability high performance device is a disk device
having a fiber channel (hereafter "FC disk device") interface, for which
is being standardized by ANSI T11. An example of a low reliability low
performance disk device is a disk device having an interface which is
different from the interface of a high reliability high performance disk
device, such as a disk device having an ATA (AT Attachment) interface
(hereafter "ATA disk device), for which is being standardized by ANSI
T13.

[0013] In the case of volume copy acquisition, the user may wish to store
the original data in the storage area of the FC disk device (hereafter
"FC storage area"), but may also wish to store the volume copy on the
storage area of the ATA disk device (hereafter "ATA storage area")
because of the cost difference.

[0014] If the original data on the FC storage area and the volume copy on
the ATA storage area are duplicated and used (that is, the FC storage
area and the ATA storage area are in a paired status) to meet the above
demand, the I/O processing performance (e.g. read or write speed of data)
between the storage control system and the host device will drop, for
example, when an I/O request (input/output request) is received from the
host device to the storage control system and then processed, because the
I/O processing performance of the FC disk device becomes equivalent to
the ATA disk device. Also the performance of the ATA disk device becomes
a bottleneck when the volume copy is acquired or when mirror
resynchronization is performed.

[0015] Such problems could occur when the attribute levels of the data
write destination storage devices, such as performance or reliability,
are apart.

SUMMARY OF THE INVENTION

[0016] With the foregoing in view, it is an object of the present
invention to minimize the influence of a storage device with a low
attribute level when storage devices with a different attribute level are
used. Specifically, to minimize the drop of processing speed when data is
synchronized among a high performance storage device and a low
performance storage device, for example.

[0017] Other objects of the present invention will be clarified by the
description herein below.

[0018] A storage control system according to a first aspect of the present
invention comprises a plurality of physical storage devices with a
different attribute level, a plurality of logical units provided on the
plurality of physical storage devices, and a control device for writing
data received from an external device to a logical unit selected from the
plurality of logical units. The plurality of logical units further
comprises one or more high level logical units provided on a physical
storage device with a high attribute level and one or more low level
logical units provided on a physical storage device with an attribute
level lower than the high attribute level. Each of the plurality of
logical units further comprises two or more chunks. The plurality of
chunks constituting the plurality of logical units further include a
plurality of high level chunks constituting the one or more high level
logical units and a plurality of low level chunks constituting the one or
more low level logical units. At least one of the plurality of high level
chunks and at least one of the plurality of low level chunks are pool
chunks that can be used dynamically. When data in a first chunk selected
from the plurality of chunks is written to a second chunk, the control
device selects either a high level chunk or a low level chunk from the
plurality of pool chunks based on the status of use of the plurality of
chunks, and writes the data in the first chunk to the selected chunk.

[0019] The first embodiment of the storage control system according to the
first aspect of the present invention further comprises a primary volume
further comprising one or more of the high level logical units selected
from the plurality of logical units, a secondary volume further
comprising one or more of the high level logical units and one or more of
the low level logical units selected from the plurality of logical units,
and a memory. The plurality of chunks include a plurality of pool chunks
and a plurality of allocated chunks. The plurality of allocated chunks
include a plurality of primary chunks constituting the primary volume,
and a plurality of secondary chunks constituting the secondary volume.
The plurality of secondary chunks include a plurality of high level
secondary chunks constituting the high level logical unit in the
secondary volume, and a plurality of low level secondary chunks
constituting the low level logical unit in the secondary volume. The
memory stores the correspondence of the primary chunk of the plurality of
primary chunks to the high level secondary chunk or the low level
secondary chunk. The control device corresponds a new secondary chunk
having an attribute level different from the secondary chunk, selected
from the plurality of pool chunks, to an original secondary chunk that is
corresponded to a primary chunk selected from the plurality of primary
chunks, and writes the data in the original secondary chunk to the new
secondary chunk, based on the status of use of the plurality of chunks
and the information stored in the memory.

[0020] The second embodiment of the storage control system according to
the first aspect of the present invention is the above mentioned first
embodiment, wherein the control device cancels the correspondence of the
original secondary chunk and the selected primary chunk after writing the
data in the original secondary chunk to the new secondary chunk, and
corresponds the new secondary chunk to the selected primary chunk in the
memory.

[0021] The third embodiment of the storage control system according to the
first aspect of the present invention is the above mentioned first
embodiment, wherein the operating condition of the plurality of chunks is
a ratio of the high level secondary volume or the low level secondary
volume in the storage capacity provided by the secondary volume.

[0022] The fourth embodiment of the storage control system according to
the first aspect of the present invention is the above mentioned third
embodiment, wherein when a threshold of a high level ratio, that is a
ratio that the plurality of high level secondary chunks occupy in the
storage capacity provided by the secondary volume, is recorded in the
memory, if the high level ratio is more than the threshold of the high
level ratio, the control device preferentially corresponds the low level
secondary chunk to the selected original secondary chunk. Or when a
threshold of a low level ratio, that is a ratio that the plurality of low
level secondary chunks occupy in the storage capacity provided by the
secondary volume, is recorded in the memory, if the low level ratio is
more than the threshold of the low level ratio, the control device
preferentially corresponds the high level secondary chunk to the selected
original secondary chunk.

[0023] The fifth embodiment of the storage control system according to the
first aspect of the present invention is the above mentioned fourth
embodiment, wherein when the data update frequency is recorded in the
memory for each of the plurality of primary chunks and the low level
secondary chunk is preferentially corresponded to the selected primary,
the control device preferentially selects the primary chunk of which the
data update frequency recorded in the memory is lower, and when the high
level secondary chunk is preferentially corresponded to the selected
primary chunk, the control device preferentially selects the primary
chunk of which the data update frequency is higher.

[0024] In the sixth embodiment of the storage control system according to
the first aspect of the present invention, when the threshold of the data
update frequency of the first chunk is recorded in the memory, the
control device corresponds a high level chunk to the first chunk if the
data update frequency is more than the threshold of the data update
frequency.

[0025] The seventh embodiment of the storage control system according to
the first aspect of the present invention is the above mentioned first
embodiment, wherein when the threshold of the data update frequency of
the primary chunk is recorded in the memory, the control device records
the data update frequency in the memory for each of the plurality of
primary chunks, and corresponds a high level chunk to the low level
secondary chunk if the data update frequency of the selected primary
chunk is more than the threshold of the data update frequency, and if a
low level secondary chunk is corresponded to the selected primary chunk.

[0026] In the eighth embodiment of the storage control system according to
the first aspect of the present invention, when the threshold of the data
update frequency of the first chunk is recorded in the memory, the
control device corresponds a low level chunk to the first chunk if the
data update frequency is less than the threshold of the data update
frequency.

[0027] The ninth embodiment of the storage control system according to the
first aspect of the present invention is the above mentioned first
embodiment, wherein when the threshold of the data update frequency of
the primary chunk is recorded in the memory, the control device records
the data update frequency in the memory for each of the plurality of
primary chunks, and corresponds a high level chunk to the low level
secondary chunk if the data update frequency of the selected primary
chunk is more than the threshold of the data update frequency, and if a
low level secondary chunk is corresponded to the selected primary chunk.

[0028] The tenth embodiment of the storage control system according to the
first aspect of the present invention is the above mentioned first
embodiment, wherein when a new primary volume, which is the same as the
primary volume, is generated, the control device corresponds a high level
chunk selected from the plurality of pool chunks to the low level
secondary chunk if it is judged from the memory that the low level
secondary chunk is corresponded to at least one of the plurality of
primary chunks, writes the data in the low level secondary chunk to the
corresponded high level chunk, and sets each of a plurality of high level
chunks, comprised of the corresponded high level chunk and one or more
high level secondary chunks corresponded to one or more primary chunks of
the plurality of primary chunks, in the memory as primary chunks.

[0029] A storage control method according to a second aspect of the
present invention is a storage control method for a storage control
system comprising a plurality of physical storage devices with a
different attribute level, and a plurality of logical units provided on
the plurality of physical storage devices. The plurality of logical units
further comprises one or more high level logical units provided on a
physical storage device with a high attribute level, and one or more low
level logical units provided on a physical storage device with an
attribute level lower than the high attribute level. Each of the
plurality of logical units further comprises two or more chunks. The
plurality of chunks constituting the plurality of logical units further
comprise a plurality of high level chunks constituting the one or more
high level logical units, and a plurality of low level chunks
constituting the one or more low level logical units. At least one of the
plurality of high level chunks and at least one of the plurality of low
level chunks are pool chunks that can be dynamically corresponded. The
storage control method comprises steps of selecting either a high level
chunk or a low level chunk from the plurality of pool chunks based on the
operating condition of the plurality of chunks when data in a first chunk
selected from the plurality of chunks is written to a second chunk, and
Writing the data in the first chunk to the selected chunk.

[0030] The first embodiment of the storage control method according to the
second aspect of the present invention is the storage control system
further comprising a primary volume further comprising one or more of the
high level logical units selected from the plurality of logical units,
and a secondary volume further comprising one or more of the high level
logical units and one or more of the low level logical units selected
from the plurality of logical units. The plurality of chunks include a
plurality of pool chunks and a plurality of allocated chunks. The
plurality of allocated chunks include a plurality of primary chunks
constituting the primary volume, and a plurality of secondary chunks
constituting the secondary volume. The plurality of secondary chunks
include a plurality of high level secondary chunks constituting the high
level logical unit in the secondary volume, and a plurality of low level
secondary chunks constituting the low level logical unit in the secondary
volume. The storage control method comprises steps of corresponding a new
secondary chunk having an attribute level different from the secondary
chunk, selected from the plurality of pool chunks, to an original
secondary chunk that is corresponded to a primary chunk selected from the
plurality of primary chunks, based on a memory that stores the
correspondence of a primary chunk of the plurality of primary chunks and
the high level secondary chunk or the low level secondary chunk, and the
operating condition of the plurality of chunks, and writing the data in
the original secondary chunk to the new secondary chunk.

[0031] The second embodiment of the storage control method according to
the second aspect of the present invention is the above mentioned first
embodiment, wherein the storage control method further comprises steps of
canceling the correspondence of the original secondary chunk and the
selected primary chunk after writing the data in the original secondary
chunk to the new secondary chunk, and corresponding the new secondary
chunk to the selected primary chunk in the memory.

[0032] The third embodiment of the storage control method according to the
second aspect of the present invention is the above mentioned first
embodiment, wherein the operating condition of the plurality of chunks is
a ratio of the high level secondary volume or the low level secondary
volume in the storage capacity provided by the secondary volume.

[0033] The fourth embodiment of the storage control method according to
the second aspect of the present invention is the storage control method
further comprising a step of corresponding a high level chunk to the
first chunk if the data update frequency is more than the threshold of
the data update frequency when the threshold of the data update frequency
of the first chunk is recorded in the memory.

[0034] The fifth embodiment of the storage control method according to the
second aspect of the present invention is the above mentioned first
embodiment, wherein the storage control method further comprises steps of
recording the data update frequency in the memory for each of the
plurality of primary chunks when the threshold of the data update
frequency of the primary chunk is recorded in the memory, and
corresponding a high level chunk to the low level secondary chunk if the
data update frequency of the selected primary chunk is more than the
threshold of the data update frequency, and if a low level secondary
chunk is corresponded to the selected primary chunk.

[0035] The sixth embodiment of the storage control method according to the
second aspect of the present invention is the storage control method
further comprising a step of corresponding a low level chunk to the first
chunk if the data update frequency is less than the threshold of the data
update frequency when the threshold of the data update frequency of the
first chunk is recorded in the memory.

[0036] The seventh embodiment of the storage control method according to
the second aspect of the present invention is the above mentioned first
embodiment, wherein the storage control method further comprises steps of
recording the data update frequency to each of a plurality of primary
chunks when the threshold of the data update frequency of the primary
chunk is recorded in the memory, and corresponding a high level chunk to
the low level secondary chunk if the data update frequency of the
selected primary chunk is more than the threshold of the data update
frequency, and if a low level secondary chunk is corresponded to the
selected primary chunk.

[0037] The eighth embodiment of the storage control method according to
the second aspect of the present invention is the storage method further
comprising steps of deciding that the low level secondary chunk is
corresponded to at least one of the plurality of primary chunks when a
new primary volume, which is the same as the above mentioned primary
volume, is generated, corresponding a high level chunk selected from the
plurality of pool chunks to the low level secondary chunk, writing data
in the low level secondary chunk to the corresponded high level chunk,
and setting each of the plurality of high level chunks, comprised of the
corresponded high level chunk and one or more high level secondary chunks
which are corresponded to each of one or more primary chunks out of the
plurality of primary chunks, in the memory as a primary chunk.

[0038] The above mentioned storage control method can be implemented in a
single storage control system, for example, or on a network where a
plurality of computers are connected. The above mentioned memory may be a
single memory, for example, or a plurality of memories. In the case of a
plurality of memories, the memories may be distributed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a diagram depicting the concept of an embodiment of the
present invention;

[0040]FIG. 2 shows a configuration example of a storage control system
according to an embodiment of the present invention;

[0053] An embodiment of the present invention will now be described with
reference to the drawings.

[0054] FIG. 1 is a diagram depicting the concept of the present
embodiment. The concept of the present embodiment will be described first
with reference to FIG. 1.

[0055] As FIG. 1 (A) shows, in the present embodiment, a plurality of
storage devices, where the attribute level of at least one of reliability
and performance is different, coexist. In the plurality of storage
devices, one or more fiber channel disk devices (hereafter "FC disk
device") 201, which are high reliability high performance disk devices,
for example, are included as storage devices with a high attribute level.
Also as a storage device with a low attribute level, one or more serial
ATA disk devices (hereafter "SATA disk device") 203, which have a low
reliability low performance but which are less expensive than the FC disk
device 201, are included. In the present embodiment, "reliability" refers
to durability which can hold data without damage and to probability of
failure which may occur, and specifically to MTBF (Mean Time Between
Failure). "Performance" refers to the value of the data transfer rate and
the speed of response.

[0056] A plurality of logical units (hereafter LU) are disposed on one or
more FC disk devices 201 and on one or more SATA disk devices 203. Each
LU is comprised of a plurality of same sized sub-LUs (hereafter called
chunks). And hereafter the LU 205 disposed on the FC disk device 201 is
called "FC-LU", and the LU 207 disposed on the SATA disk device 203 is
called "SATA-LU". The chunk constituting the FC-LU 205 is called
"FC-chunk", and the chunk constituting the FC-LU 206 is called
"SATA-chunk". In FIG. 1, the FC-chunk is indicated by a blank frame, and
the SATA-chunk is indicated by a hatched frame.

[0057] In the present embodiment, one virtual LU is comprised of one or
more LUs. A virtual LU is also called a "logical volume". In the present
embodiment, a virtual LU is either a primary volume (hereafter PVOL) 204
or a secondary volume (hereafter SVOL) 206, for example. The PVOL 204 is
comprised of one or more FC-LUs 205. The SVOL 206, on the other hand, may
be comprised of only one or more FC-LUs 205 or only one or more SATA-LUs
207, or a combination of FC-LU 205 and SATA-LU 207. Hereafter the FC-LU
205 constituting the PVOL 204 is called the "PVOL-FC-LU 205", and the
FC-chunk constituting the PVOL 204 is called the "PVOL-FC-chunk". The
FC-LU 205 constituting the SVOL 206 is called the "SVOL-FC-LU 205", the
SATA-LU 207 constituting the SVOL 206 is called the "SVOL-SATA-LU-207",
the FC-chunk constituting the SVOL 206 is called the "SVOL-FC-chunk", and
the SATA-chunk constituting the SVOL 206 is called the "SVOL-SATA-chunk".
The SVOL-FC-chunk and the SVOL-SATA-chunk may commonly be called the
"SVOL-chunk".

[0058] In the present embodiment, the storage control program can perform
management by duplicating of PVOL 204 and SVOL 206, and in this case,
when the data from the host device is written to the PVOL 204, for
example, the same data can be written to the SVOL 206. Specifically, in
the storage control system, the PVOL-FC-chunk and the SVOL-FC-chunk or
the SVOL-SATA-chunk are duplicated and managed, and when sub-data (one
composing element of data) is written to a PVOL-FC-chunk, the same
sub-data is also written to the duplicated SVOL-FC-chunk or
SVOL-SATA-chunk. Hereafter storing the same data to the PVOL 204 and the
SVOL 206 is called "mirroring", a pair of PVOL 204 and SVOL 206 is called
a "volume pair", and a pair of PVOL-FC-chunk and SVOL-FC-chunk or
SVOL-SATA-chunk is called a "chunk pair".

[0059] In the present embodiment, other than the PVOL-FC-chunk,
SVOL-FC-chunk and SVOL-SATA-chunk, a pool chunk group 208, comprised of a
plurality of pool chunks which belong to neither PVOL 204 nor SVOL 206,
exists. The plurality of pool chunks constituting the pool chunk group
208 includes a "pool-FC-chunk" which is an FC-chunk, and a
"pool-SATA-chunk" which is an SATA-chunk. The storage control system
selects a pool chunk from the pool chunk group 208, allocates it to an
SVOL-chunk, copies the sub-data in the SVOL-chunk to the selected pool
chunk, sets the pool chunk as SVOL-chunk, and sets the SVOL-chunk, which
is the copy source of the sub-data, as a pool chunk, so as to exchange
the pool chunk and SVOL-chunk. Allocation of pool chunks to the
SVOL-chunk can be determined depending on variety of policy, for example,
the update frequency of sub-data in the PVOL-chunk which is chunk pair
partner of the SVOL-chunk.

[0060] Specifically, in the case when the PVOL-FC-chunk "#2" and
SVOL-FC-chunk "2" form a chunk pair, as shown in FIG. 1 (A), for example,
if it is detected that the update frequency of the sub-data in the
PVOL-FC-chunk "#2" is lower than a predetermined threshold, the storage
control system selects a pool SATA-chunk (e.g. #51'') from the pool chunk
group 208, and copies the sub-data B in the SVOL-FC-chunk "#2" to the
selected pool SATA-chunk "#51". And, as shown in FIG. 1 (B), the storage
control system sets the pool SATA-chunk "#51" as SVOL-FC-chunk "#51"
instead of SVOL-FC chunk "#2", and sets the SVOL-FC-chunk "#2" as the
pool SATA-chunk "#2" instead of the pool SATA-chunk "#51". In this way,
if it is detected that the chunk pair partner of PVOL-FC-chunk, of which
update frequency of the sub-data is lower than the predetermined
threshold, is the SVOL-FC-chunk, then the chunk pair partner of the
PVOL-FC-chunk is switched from the SVOL-FC-chunk to the pool SATA-chunk
(after swap, the pool SATA-chunk becomes the SVOL-SATA-chunk).

[0061] Also, in the case when PVOL-FC-chunk "#8" and SVOL-SATA-chunk "#4"
form a chunk pair, as shown in FIG. 1 (A), for example, if it is detected
that the update frequency of the sub-data in PVOL-FC-chunk "#8" is higher
than the predetermined threshold, the storage control system selects the
pool FC-chunk (e.g. "#53") from the pool chunk group 208, and copies the
sub-data H in the SVOL-SATA-chunk "#4" to the selected pool FC-chunk
"#53". And the storage control system sets the pool FC-chunk "#53" as
SVOL-FC-chunk "#53" instead of SVOL-SATA-chunk "#4", and sets the
SVOL-SATA-chunk "#4" as the pool SATA-chunk "#4" instead of the pool
FC-chunk "#53". In this way, when it is detected that the chunk pair
partner of the PVOL-FC-chunk, of which the update frequency of the
sub-data is higher than the predetermined threshold, is the SVOL-SATA
chunk, then the chunk pair partner of the PVOL-FC-chunk is switched from
the SVOL-SATA-chunk to the pool FC-chunk (after swap, the pool FC-chunk
becomes the SVOL-FC-chunk).

[0062] The above is the description on the concept of the present
embodiment. In the description herein below, it is assumed that one or
more FC-LUs 205 constituting the PVOL 204 and one or more FC-LUs 205 and
SATA-LU 207 constituting the SVOL 206 exist in a same storage control
system, but these may be distributed in a plurality of systems.

[0063] Now the present embodiment will be described.

[0064]FIG. 2 shows a configuration example of the storage control system
according to the present embodiment.

[0065] The storage control system 200 is comprised of one or more fiber
channel interface devices (hereafter fiber I/F) 290A and 290B (this is
not limited to an FC interface device, but may be another interface
device). For example, a host device 100, such as a personal computer, may
be connected to the fiber I/F 290A, and a backup server 400 having a tape
device (e.g. magnetic tape recording device) 500 may be connected to the
fiber I/F 290B. The backup server 400 reads data in the SVOL 206 via the
fiber I/F 290B, and writes the data to the tape device 500. If the data
in the SVOL 206 is updated during backup, data consistency is lost, so
the storage control system 200 does not allow backup by the backup server
400 during mirroring. A case of when backup is allowed, for example, is
allowing a data update from the host device 100 to the PVOL 204, but not
to the SVOL 206, which is a non-mirroring status.

[0066] The storage control system 200 comprises a management interface
(hereafter management I/F) 240, such as a LAN controller, for example. A
management terminal 600, for managing the storage control system 200, is
connected to the management I/F 240.

[0067] The storage control system 200 is comprised of a plurality of disk
devices 201 and 203, a disk controller 250 for controlling the plurality
of disk devices 201 and 203, a cache memory 230 for temporarily storing
data to be exchanged between an external device (e.g. host device 100)
and the disk devices 201 and 203, a CPU 210 for controlling operation of
the storage control system 200, and a control memory 220 for storing a
computer program to be read by the CPU 210 and such control information
as a table which is referred to by the CPU 210.

[0068] The plurality of disk devices 201 and 203 include one or more FC
disk devices 201 and one or more SATA disk device 203. The one or more FC
disk devices 201 has a plurality of FC-LUs 205, as mentioned above. Each
FC-LU 205 can be a composing element of the PVOL 204 or can be a
composing element of the SVOL 206. The one or more SATA disk devices 203,
on the other hand, has one or more SATA-LUs 207, as mentioned above. The
SATA-LU 207 can be a composing element of the SVOL 206. In the
illustrated example, one FC-LU 205 constitutes the PVOL 204, and one
FC-LU 205 and one SATA-LU 207 constitute the SVOL 206.

[0070] The basic control program 301 is a computer program for controlling
the basic operation of the storage control system 200. For example, the
basic control program 301 reads data from the LU 205 and 206A or 206B
according to the I/O request from the host device 100, and sends it to
the host device 100 via the cache memory 230, or stores the data included
in the I/O request in the first LU 205.

[0071] The volume copy acquisition program 302 is a computer program for
executing volume copy acquisition.

[0072] The update frequency threshold swap program 303 selects the type of
chunk (in other words, either pool FC-chunk or pool SATA-chunk) to be the
data swap partner of the SVOL-chunk corresponded to the PVOL-FC chunk,
based on whether the update frequency of the PVOL-FC chunk is over the
predetermined update frequency threshold.

[0073] The disk usage ratio swap program 304 selects the type of chunk (in
other words, either pool FC-chunk or pool SATA-chunk) to be the copy
destination of the sub-data of the SVOL-chunk, based on whether the ratio
of the SVOL-FC-chunk (or SVOL-SATA-chunk) in the SVOL 206 is over the
predetermined ratio.

[0074] The failure swap program 305 switches the SVOL-FC-chunk
corresponding to the PVOL-FC-chunk to the PVOL-FC chunk when a failure
occurs to the PVOL 204 (e.g. when the FC disk device having the
PVOL-FC-LU is damaged). When failure occurs to the PVOL 204 and if the
SVOL-SATA-chunk corresponding to the PVOL-FC-chunk exists in the SVOL
207, the failure swap program 305 moves the sub-data in the
SVOL-SATA-chunk to the pool FC-chunk selected from the pool chunk group
208, and switches the pool FC-chunk to the PVOL-FC-chunk. In this way,
when failure occurs to the PVOL 204, the failure swap program 305
constructs a new PVOL by the SVOL-FC-chunk corresponding to the
PVOL-FC-chunk and the pool FC-chunk allocated to the SVOL-SATA-chunk
corresponding to the PVOL-FC-chunk.

[0075] Now each table 309-306 and 911, which are stored in the control
memory 220, will be described with reference to FIG. 3 to FIG. 6.

[0077] The volume copy LU registration table 309 is a table where the
information on a plurality of LUs in the storage control system 200 is
registered. Specifically, in the volume copy LU registration table 309, a
pair number, external LU number, internal LU number, LU capacity, disk
type, PVOL/SVOL information and access attribute are registered for each
of the plurality of LUs.

[0078] The pair number is an identification number of the volume pair.

[0079] The external LU number is an LU number received from an external
device, such as a host device. When two or more LUs are provided to the
external device as one logical volume, the external LU number becomes a
same number for these two or more LUs. In the case of this example, if
"2" is specified from the external device as an LU number, the LU with
the internal LU number "2" and the LU with the internal LU number "3" are
provided to the external device as one SVOL 206.

[0080] The internal LU number is an LU number which the storage control
system 200 recognizes and manages. In this embodiment, the LU with the
internal LU number "1", for example, is PVOL-FC-LU 205, and the LU with
the internal LU number "2" is SVOL-FC-LU 205, and the LU with the
internal LU number "3" is SVOL-SATA-LU 207.

[0081] The LU capacity is a storage capacity of an LU.

[0082] The disk type is a type of disk device which has the corresponding
LU (e.g. interface). Specifically, a disk type indicates either an FC
disk device or an SATA disk device.

[0083] PVOL/SVOL information is information to indicate whether the
corresponding LU constitutes a PVOL or an SVOL.

[0084] The access attribute is information to indicate what kind of access
is enabled to the corresponding LU. For example, "R/W enable" indicates
that both read and write are enabled, "R only" indicates that read is
enabled but that write is disabled, "W only" indicates that write is
enabled but that read is disabled, and "R/W disable", which is not shown
in the drawing, indicates that both read and write are disabled. Various
types can be used for the access attribute.

[0086] In the LU management table 911, a plurality of LU information
items, corresponding to the plurality of LUs existing in the storage
control system 200 respectively, is registered. The LU information
includes such LU information elements as the internal LU # (number), LU
capacity, disk type, selectability information and pool chunk #. Here the
selectability information is information that indicates if the LU can be
selected or not when a volume copy pair is being set ("volume copy" is a
stored image of data at a certain point of time). The pool chunk # is a
number assigned to a chunk for which the kind of chunk and how the chunk
will be used is not defined, and which can be dynamically allocated
(therefore it is a pool chunk).

[0087]FIG. 4 is a configuration example of a volume copy management
table.

[0088] The volume copy management table 308 is a table for managing
original data and information on volume copy. The volume copy management
table 308 is largely divided into a left column, middle column and right
column.

[0089] In the left column, information on PVOL 204, which stores original
data, is registered. Specifically, in the left column, the LU #, chunk #
and update frequency, for example, are registered for each chunk
constituting the PVOL 204. The LU # is an internal LU number of an LU
which has a corresponding chunk, and is registered as a PVOL. The chunk #
is a serial number of the chunk assigned within an LU. For example, the
minimum value of a chunk # is 1, and the maximum value of a chunk # is a
value of the quotient obtained when the LU capacity of an LU having a
corresponding chunk is divided by the chunk size (the quotient is rounded
up if a remainder is generated). The update frequency is a number of
times when the sub-data stored in the corresponding chunk is updated, and
the initial value is 0. The update frequency is incremented or reset by
the CPU 210, for example.

[0090] In the middle column, information on an SVOL 206 for storing the
volume copy is registered. Specifically, in the middle column, a disk
type, LU # and chunk #, for example, are registered for each chunk
constituting an SVOL 206. The disk type is a type of disk device (e.g.
interface type) which has an LU having a corresponding chunk. The LU # is
an internal LU number of an LU which has a corresponding chunk, and is
registered as an SVOL. The chunk # is a serial number of the chunk
assigned within the LU. Each row in this middle column corresponds to
each row of the left column. In other words, information on a
PVOL-FC-chunk is registered in the rows of the left column, and in each
row of the middle column, information on an SVOL-chunk (specifically,
either an SVOL-FC-chunk or an SVOL-SATA-chunk) is registered.

[0091] In the right column, information on a swap partner chunk is
registered. Here "swap partner chunk" is a chunk to be the swap
destination (in other words the shift destination) of the sub-data in the
corresponding SVOL-chunk. In this right column, the disk type, LU# and
chunk # are registered for each swap partner chunk. As a swap partner
chunk, a pool chunk, which has not yet been decided how to be used as a
chunk, can be allocated. A blank means that an SVOL-chunk has no swap
partner chunk.

[0092] The CPU 210 refers to this volume copy management table 308, and
can identify the following. For example, the CPU 210 can identify that an
FC-chunk with LU # "2" and chunk # "1" is corresponded to the
PVOL-FC-chunk with LU # "1" and chunk # "1" as an SVOL chunk. And the CPU
210 can also identify that a pool SATA-chunk with LU # "3` and chunk #
"5" is corresponded to the SVOL-chunk as the swap partner chunk.

[0093] The above is a configuration example of the volume copy management
table 308. In the volume copy management table 308, a plurality of
SVOL-chunks may be corresponded to one PVOL-FC-chunk, or a plurality of
swap partner chunks may be corresponded to one SVOL-chunk.

[0095] In the setup value table 307, information can be input and
registered from the management terminal 600, for example. The chunk size,
swap period, update frequency threshold and disk ratio threshold, for
example, are registered in the setup value table 307.

[0096] The chunk size is a value for driving an LU into a certain number
of byte units to be chunks. The swap period is a value for indicating the
schedule to swap the data stored in an SVOL-chunk with a pool FC-chunk or
pool SATA-chunk, based on the update frequency threshold or disk ratio
threshold (e.g. "weekly" if this is to be done once every week).

[0097] The update frequency threshold is a threshold for deciding whether
the sub-data in an SVOL-chunk corresponding to a PVOL-FC-chunk is stored
in a pool chunk. This update frequency threshold is a value to be
compared with the number of times sub-data in a PVOL-FC-chunk was updated
during the above mentioned swap period (that is, the update frequency
recorded in the volume copy management table 308) by the write command
from an external device.

[0098] The disk ratio threshold is a threshold of the ratio of the storage
capacity created by one or more SVOL-FC-chunks (hereafter SVOL-FC storage
capacity) in an entire SVOL 206. Specifically, if the disk ratio
threshold is "0.3", for example, the SVOL-FC storage capacity is 0.3
(that is 30%) in an entire SVOL 206, which means that the storage
capacity created by one or more SVOL-SATA-chunks (hereafter SVOL-SATA
storage capacity) is the remaining 0.7 (that is 70%) in an entire SVOL
206.

[0099] A plurality of setup value tables corresponding to the plurality of
pair numbers (that is a plurality of volume pairs) may be provided. In
this case, the CPU 210 of the storage control system 200 may perform
management referring to the setup value tables corresponding to each pair
number. This increases flexibility of management.

[0101] The failure handling volume copy management table 306 is a table
for managing which FC-chunk, corresponding to each PVOL-FC chunk in a
PVOL 204, is switched to a PVOL-FC-chunk when a failure occurred to the
PVOL 204. The failure handling volume copy management table 306 is
largely divided into a left column, middle column and right column, just
like the volume copy management table 308. The left column has the same
configuration of the left column of the volume copy management table 308,
except that the update frequency is not registered in this case. The
middle column has the same configuration as the middle column of the
volume copy management table 308.

[0102] In the right column, information on the failure handling shift
destination chunk is registered. Here "failure handling shift destination
chunk" is a chunk selected from the pool chunk group 208 as a shift
destination of the sub-data in an SVOL-chunk. In the right column, the
disk type, LU # and chunk # are registered for each failure handling
shift destination chunk. As FIG. 6 shows, the failure handling shift
destination chunk is an FC-chunk in the present embodiment, and the
SVOL-chunk corresponded to the failure handling shift destination chunk
is an SVOL-SATA chunk. By this, when a failure occurs in a PVOL 204, and
if a copy of the sub-data in the PVOL-FC-chunk exists in the
SVOL-SATA-chunk, the sub-data in the SVOL-SATA-chunk is shifted to the
FC-chunk corresponded to the SVOL-SATA-chunk (that is, an open chunk on
the FC disk device, which is a high reliability high performance disk
device). A blank indicates that a failure handling shift destination
chunk in an SVOL-chunk is not corresponded.

[0103] The above is the description on each table 309-306 and 911 which
are stored in the control memory 220.

[0104] Now the processing flow to be executed in the present embodiment
will be described below with reference to the above mentioned tables
309-306 and 911.

[0105]FIG. 7 shows a processing flow to be executed by the volume copy
acquisition program 302 which is read by the CPU 210.

[0106] The volume copy acquisition program 302 sets a pair of volume copy
(step S1). In this case, information is registered in the volume copy LU
registration table 309 according to the flow shown in FIG. 11, for
example.

[0107] For example, the volume copy acquisition program 302 displays the
copy pair setup screen 912 on the display screen of the management
terminal 600. The LU # (internal LU number) of the PVOL-LU constituting
the PVOL 204 and the LU # of a plurality of SVOL-LUs (one or more FC-LU
and one or more SATA-LU) constituting the SVOL are input in the copy pair
setup screen 912. When PVOL-FC-LU (FC-LU constituting the PVOL 204),
SVOL-FC-LU (FC-LU constituting the SVOL 206) and SVOL-SATA-LU (SATA-LU
constituting the SVOL 206) are selected from the plurality of LUs not
registered in the volume copy LU registration table 309 (in other words,
LUs which are selectable in the LU management table 911), the respective
LU #s are input in this copy pair setup screen 912, and the volume copy
acquisition program 302 writes each LU # which was input to the volume
copy LU registration table 309. The volume copy acquisition program 302
also acquires other LU information elements (e.g. disk type)
corresponding to the LU #, which was input, from the LU management table
911, and writes the acquired LU information elements to the volume copy
LU registration table 309. For example, if the internal LU # "1" is input
as the PVOL-FC-LU, the internal LU # "2" is input as the SVOL-FC-LU, and
the internal LU # "3" is input as the SVOL-SATA-LU, then in the LU
management table 911, the volume copy acquisition program 302 switches
the selectability information corresponding to each internal LU # "1"-"3"
from selectable to unselectable, and constructs the volume copy LU
registration table 309 shown in FIG. 3.

[0108] Now S2 and later processing will be described with reference again
to FIG. 7.

[0109] The volume copy acquisition program 302 receives input of the
values of the setup value table 307 from the user via the management
terminal 600, for example. When various values (that is chunk size, swap
period, update frequency threshold and disk ratio threshold) are input,
the volume copy acquisition program 302 registers the values, that were
input, in the setup value table 307 (S2).

[0110] Then the volume copy acquisition program 302 registers the
PVOL-FC-chunk in the volume copy management table 308 (S3). A specific
example of this processing will be described with reference to FIG. 12
(A). For example, the volume copy acquisition program 302 calculates the
number of chunks based on the LU capacity and the chunk size registered
in the setup value table 307, for the PVOL-FC-LU which is set in the
volume copy LU registration table 309. And the volume copy acquisition
program 302 assigns the chunk # as a serial number to the calculated
number of chunks respectively, and registers the assigned chunk # and the
LU # of the PVOL-FC-LU thereof in the volume copy LU registration table
309. The volume copy acquisition program 302 inputs "0" to the update
frequency of each PVOL-FC-chunk as an initial value. When data is updated
by a write command from an external device, such as the host device 100,
the volume copy acquisition program 302 adds "1" to the update frequency
corresponding to the PVOL-FC-chunk for which data was updated.

[0111] Then the volume copy acquisition program 302 registers the
SVOL-FC-chunk in the volume copy management table 308 (S4). A specific
example of this processing will be described with reference to FIG. 12
(B). For example, the volume copy acquisition program 302 calculates the
number of chunks of the PVOL-FC-LU and assigns a chunk # to each chunk in
a same method as the case of registering the PVOL-FC-chunk, and registers
the assigned chunk # and the LU # of the SVOL-FC-LU thereof in the volume
copy LU registration table 309.

[0112] If an SVOL-chunk was set for all the PVOL-FC-chunks in S4 (Y in
S5), the volume copy acquisition program 302 moves to S1 without
executing the later mentioned operations in S6-S10.

[0113] When the SVOL-chunk is not set for at least one PVOL-FC-chunk, and
the SVOL-FC-chunk remains without being corresponded with the
PVOL-FC-chunk in S4 (N in S5 and Y in S6), the volume copy acquisition
program 302 executes the operation in S4 for the remaining PVOL-FC-chunk.

[0114] When the SVOL-chunk is not set for at least one PVOL-FC-chunk and
SVOL-FC-chunks do not remain (N in S5 and N in S6) in S4, the volume copy
acquisition program 302 calculates the number of chunks for SVOL-SATA-LU
and assigns a chunk # to each chunk, just like the case of SVOL-FC-LU,
and registers the allocated chunk # and LU # in the volume copy LU
registration table 309 (S7). FIG. 12 (C) shows an example of this result.

[0115] When the SVOL-chunk is set for all the PVOL-FC-chunks in S7 (Y in
S8), the volume copy acquisition program 302 moves to S11 without
executing the later mentioned operations in S9-S10.

[0116] When the SVOL-chunk is not set for at least one PVOL-chunk and the
SVOL-SATA-chunk remains without being corresponded to the PVOL-FC-chunk
in S7 (N in S8 and Y in S9), the volume copy acquisition program 302
returns to the beginning of S7.

[0117] When the SVOL-chunk is not set for at least one PVOL-FC-chunk and
selectable SVOL-SATA-chunk does not remain at S7 (N in S8 and N in S9),
the volume copy acquisition program 302 outputs a warning, to add an LU
to SVOL, on the management terminal 600, for example (S10), because this
means that the number of chunks of SVOL are insufficient.

[0118] If data is stored in PVOL after Y in S5 and Y in S8, the volume
copy acquisition program 302 judges the correspondence of the chunk of
PVOL and the chunk of SVOL referring to the volume copy management table
308, and stores the sub-data in the PVOL-FC-chunk and the SVOL-chunk
corresponded thereto (S11). Specifically, the volume copy acquisition
program 302 duplicates the sub-data registered in the cache memory 230,
stores one sub-data on the cache memory 230 in the PVOL-FC-chunk, and
stores the other sub-data on the cache memory 230 in the SVOL-chunk
corresponded to that PVOL-FC-chunk.

[0119] After S11, the volume copy acquisition program 302 sets the access
attribute of each LU constituting the SVOL to R/W enable (enabling both
read and write) in the volume copy LU registration table 309 at an
arbitrary timing (S12).

[0120] In this processing, data may be written to the PVOL by random write
access, or data may be written by sequential write access. In the case of
random write access, for example, the volume copy acquisition program 302
receives a corresponding write command for each PVOL-FC-chunk, and stores
the sub-data to the PVOL-FC-chunk and the SVOL-chunk corresponded thereto
each time one write command is processed. In the case of sequential write
access, for example, the volume copy acquisition program 302 receives
write commands corresponding to a plurality of PVOL-FC-chunks (e.g. all
the PVOL-FC-chunks), and when one write command is processed, sub-data is
written to the plurality of PVOL-FC-chunks and the plurality of
SVOL-chunks corresponding thereto sequentially from a smaller chunk #.

[0121]FIG. 8 shows the processing flow to be executed by the update
frequency threshold swap program 303 which is read by the CPU 210.

[0122] When the time of the swap period registered in the setup value
table 307 comes (S21-A), or when the user inputs a data swap instruction
via a predetermined terminal (e.g. management terminal 600 or host device
100) (S21-B), the basic control program 301 starts up the update
frequency threshold swap program 303.

[0123] When it is detected that the volume pair selected from one or more
volume pairs (hereafter target volume pair (s)) are in non-mirror status,
the update frequency threshold swap program 303 sets the access attribute
of each LU constituting the SVOL of the target volume pair to update
disable (e.g. R only) in the volume copy LU registration table 309. When
the target volume pair is in mirror status, a warning is output (S22).
Whether the target volume pair is non-mirror status or mirror status can
be judged by referring to the pair management table 914 (e.g. provided in
the control memory 220) in which the status information corresponding to
each pair number (information to indicate mirror status or non-mirror
status) is registered. Mirror status is a status where data is
duplicated. In other words, in this status if data is updated in the
PVOL, the same updated data is copied to the SVOL (in other words, the
SVOL is synchronized with the PVOL). Non-mirror status is a status where
duplication is not being done, in other words, in this status even if
data is updated in the PVOL, the updated data is not written to the SVOL
(in other words, the SVOL is not synchronized with the PVOL).

[0124] The update frequency threshold swap program 303 compares the update
frequency of the PVOL-chunk registered in the first row of the volume
copy management table 308 and the update frequency threshold registered
in the setup value table 307 (S23).

[0125] When it is judged that the update frequency of the PVOL-FC-chunk is
the update frequency threshold or more (Y in S23) and the SVOL-chunk of
the chunk pair partner of the PVOL-FC-chunk is an FC-chunk based on the
judgment according to the volume copy management table 308 (Y in S24) in
S23, the update frequency threshold swap program 303 advances to the
later mentioned S28.

[0126] When the update frequency of the PVOL-FC-chunk is the update
frequency threshold or more (Y in S23) and the SVOL-chunk corresponding
to the PVOL-FC-chunk is not an FC-chunk based on the judgment according
to the volume copy management table 308 (N in S24) in S23, the update
frequency threshold swap program 303 selects a pool FC-chunk from the
plurality of pool chunks, and writes the chunk # and LU # of the selected
pool FC-chunk to the right column (column of the swap partner chunk) of
the volume copy management table 308 with corresponding to the SVOL-chunk
which is not the above FC-chunk (that is, SVOL-SATA-chunk) (S25). By this
for the SVOL-SATA-chunk corresponded to the PVOL-FC-chunk of which the
update frequency of the sub-data is the update frequency threshold or
more, the FC-chunk existing on a high reliability high performance disk
device is corresponded as the data swap partner. The chunk # corresponded
to the SVOL-SATA-chunk is selected from a plurality of pool chunks,
therefore it is a chunk # not registered on the volume copy management
table 308.

[0127] When the update frequency of the PVOL-FC-chunk is less than the
update frequency threshold (N in S23) and the SVOL-chunk corresponding to
the PVOL-FC-chunk is an SATA-chunk based on the judgment according to the
volume copy management table 308 (Y in S26) in S23, the update frequency
threshold swap program 303 advances to the later mentioned S28.

[0128] When the update frequency of the PVOL-FC-chunk is less than the
update frequency threshold (N in S23) and the SVOL-chunk corresponding to
the PVOL-FC-chunk is not an SATA-chunk (N in S26) based on the judgment
according to the volume copy management table 308 in S23, the update
frequency threshold swap program 303 selects the SATA-chunk from a
plurality of pool chunks, and writes the chunk # and LU # of the selected
SATA-chunk to the right column (column of the swap partner chunk) of the
volume copy management table 308 with corresponding to the SVOL-chunk
which is not the above SATA-chunk (that is the SVOL-FC-chunk) (S27). By
this, for the SVOL-FC-chunk corresponded to the PVOL-FC-chunk of which
the update frequency of the sub-data is less than the update frequency
threshold, the SATA-chunk existing on a low reliability low performance
but inexpensive disk device is corresponded as the data swap partner.

[0129] In the case of Y in S24, Y in S26 and a chunk existing in the swap
destination (that is, a selectable pool chunk does not exist) in S25 or
S27 (N in S28), the pools of chunks at the swap destination are
insufficient, so the update frequency threshold swap program 303 outputs
a warning, to have the SVOL add an LU or change the threshold, to the
management terminal 600 or host device 100, for example (S29). The later
mentioned processings in S31-S36 may be executed without confirming all
the chunks. In this case, processing in S22 or later may be executed
after these processings.

[0130] When the swap destination chunks are sufficient in S28 (Y in S28),
the update frequency threshold swap program 303 judges whether the
comparison processing of the update frequency and the update frequency
threshold has been completed for all the PVOL-FC-chunks (S30).

[0131] If there is a PVOL-FC-chunk for which comparison processing has not
been executed in S30 (N in S30), the update frequency threshold swap
program 303 returns to S23, and executes the processings in S23-S28 for
the next PVOL-FC-chunk.

[0132] If it is judged that the comparison processing has been completed
for all the PVOL-FC-chunks in S30 (Y in S30), the update frequency
threshold swap program 303 judges whether data is being read from the
SVOL by backup so as to execute processing to swap data in the
corresponding copy destination chunk to the swap destination chunk having
the chunk # registered in the volume copy management table 308 (S31).

[0133] When data is being read from the SVOL in S31 (Y in S31), the update
frequency threshold swap program 303 outputs a warning to stop the
reading operation, such as backup, or to stop the swap program (S32).

[0134] When data is not being read from the SVOL in S31 (N in S31), the
update frequency threshold swap program 303 sets the access attribute of
each LU constituting the SVOL to read disable (e.g. R/W disabled) (S33).

[0135] After S33, the update frequency threshold swap program 303 shifts
the sub-data in the SVOL-chunk having a chunk # registered in the middle
column (SVOL column) to the swap destination chunk corresponded to the
SVOL-chunk based on the volume copy management table 308 (S34). When this
completes, the update frequency threshold swap program 303 overwrites the
content of the swap destination chunk (disk type, LU # and chunk #) on
the content of the SVOL-chunk corresponding to the swap destination chunk
in the volume copy management table 308, and deletes the content of the
swap destination chunk from the right column (swap partner chunk column)
(S35). In this case, the update frequency threshold swap program 303 may
register the deleted content of the swap destination chunk (e.g. chunk #)
to the LU management table 911, for example, as a content of a pool
chunk.

[0136] After S35, the update frequency threshold swap program 303 sets the
access attribute of each LU constituting the SVOL to read enable (e.g. R
only) (S36). After S36, if processing after S31 had been executed without
performing the above comparison processing for all the PVOL-FC-chunks,
the update frequency threshold swap program 303 returns to S3, as shown
by the dotted line.

[0137] After S36, the update frequency threshold swap program 303 resets
the update frequency of each v on the volume copy management table 308 to
the initial value (S37). And the update frequency threshold swap program
303 sets the access attribute of each LU constituting the SVOL to
updatable (e.g. R/W enabled) (S38).

[0138] The above is the processing flow to be executed by the update
frequency threshold swap program 303.

[0139]FIG. 9 shows the processing flow to be executed by the disk usage
ratio swap program 304 which is read by the CPU 210.

[0140] When the swap period registered in the setup value table 307 comes
(S41-A), or when the user inputs a data swap instruction via a
predetermined terminal (e.g. management terminal 600 or host device 100)
(S41-B), the basic control program 301 starts up the disk usage ratio
swap program 304.

[0141] The disk usage ratio swap program 304 sets the access attribute of
each LU constituting the SVOL of the target volume pair to update disable
(e.g. R only) in the volume copy LU registration table 309 with the same
method as S22 in FIG. 8 (S42).

[0142] Then the disk usage ratio swap program 304 sorts a plurality of
rows on the volume copy management table 308 in the descending order of
data update frequency (S43). Hereafter the number of rows in the volume
copy management table 308 is assumed to be n and the row number after the
above sorting is i, and the volume copy management table 308 after the
above sorting is P (i). The disk usage ratio swap program 304 executes
the following S44 and the later processings in the sequence of lower row
number i after the sorting (in other words, starting from the higher data
update frequency).

[0143] The disk usage ratio swap program 304 selects one row number i from
the plurality of row numbers after the above sorting, and compares the
value i/n when the selected row number i is divided by the number of rows
n and the disk ratio threshold T registered in the setup value table 307
(S44).

[0144] When i/n is T or more as a result of S44, the disk usage ratio swap
program 304 judges whether the SVOL-chunk corresponding to the
PVOL-FC-chunk with the above selected row number i is an FC-chunk or not
(S45). In S45, if a positive judgment result is acquired (Y in S45), the
disk usage ratio swap program 304 executes the later mentioned processing
in S51. If a negative judgment result is acquired in S45 (N in S45), the
disk usage ratio swap program 304 selects an FC-chunk from a plurality of
pool chunks, and sets the selected FC-chunk in P(i) as a swap partner
chunk of the above mentioned corresponded SVOL-chunk (S46). At this time,
if a selectable FC-chunk does not exist in the plurality of pool chunks
(N in S49), the disk usage ratio swap program 304 outputs a warning, to
increase the selectable pool FC-chunks, to the user (S50), and if not
executes S51 (Y in S49).

[0145] When i/n is less than T as a result of S44, the disk usage ratio
swap program 304 judges whether the SVOL-chunk corresponding to the
PVOL-FC-chunk with the above mentioned selected row number i is an
SATA-chunk or not (S47). In S45, if a positive judgment result is
acquired (Y in S47), the disk usage ratio swap program 304 executes the
later mentioned processing in S51. If a negative judgment result is
acquired in S47 (N in S47), the disk usage ratio swap program 304 selects
an SATA-chunk from a plurality of pool chunks, and sets the selected
SATA-chunk in P (i) as a swap partner chunk of the above mentioned
corresponded SVOL-chunk (S48). At this time, if a selectable SATA-chunk
does not exist in the plurality of pool chunks (N in S49), the disk usage
ratio swap program 304 outputs a warning, to increase the selectable pool
SATA-chunks, to the user (S50), and if not executes S51 (Y in S49).

[0146] The disk usage ratio swap program 304 executes the above mentioned
processings in S44-S48 for all the row numbers i (N in S51), and when
this processing is completed for all the row numbers i (Y in S51), the
same processing as S31-S38 in FIG. 8 are executed.

[0147] In the above processing flow, if the SVOL-chunk corresponding to
the PVOL-FC-chunk is not a chunk with an appropriate attribute level
according to the update frequency of the sub-data in the PVOL-FC-chunk,
the sub-data in the SVOL-chunk is shifted to another chunk with an
appropriate attribute level, and the ratio of the SVOL-FC storage
capacity in SVOL 206 (in other words, the ratio of the SVOL-SATA storage
capacity) is adjusted to the disk ratio threshold T.

[0148]FIG. 10 shows the processing flow to be executed by the failure
swap program 305 which is read by the CPU 210. In the description below,
to make the description simple and clear, the PVOL when failure occurs is
called the "original PVOL", the SVOL when failure occurs is called the
"original SVOL", and the PVOL and SVOL created by the failure swap
program are called the "new PVOL" and the "new SVOL" respectively. Also
in the description below, it is assumed that a failure occurred to the
original PVOL, while the write data received from the host device 100 is
being written to the original PVOL.

[0149] When a failure occurs to the original PVOL (S61), the basic control
program 301 detects this, and starts up the failure swap program 305.

[0150] The failure swap program 305 sets the access attribute of each LU
constituting the original PVOL where a failure occurred to read disable
(e.g. R/W disable) in the volume copy LU registration table 309 (S62).
The failure swap program 305 saves the write data from the host device
100 to the original PVOL in the cache memory 230 or in another LU (S63).

[0151] Then the failure swap program 305 selects an FC-chunk out of a
plurality of pool chunks, and writes the chunk # and LU # of the selected
FC-chunk in the right column of the failure handling management table 306
(failure handling shift destination chunk column) with corresponding to
the original SVOL-SATA-chunk (S64). At this time, if there are sufficient
allocatable FC-chunks (Y in S65), the failure swap program 305 executes
the later mentioned S67, and if no allocatable FC-chunk exists in the
plurality of pool chunks, the failure swap program 305 outputs a warning
to notify that FC-LU is insufficient (N in S65 and S66).

[0152] In S67, the failure swap program 305 shifts the sub-data in the
original SVOL-SATA-chunk, having a chunk # registered in the middle
column (SVOL column), to the swap destination chunk (FC-chunk)
corresponded to that original SVOL-SATA-chunk, based on the failure
handling volume copy management table 306 (S67).

[0153] Then the failure swap program 305 overwrites the content (LU # and
chunk #) of the swap destination chunk on the content of the original
PVOL-FC-chunk corresponding to that swap destination chunk in the failure
handling volume copy management table 306, and deletes the content of the
swap destination chunk. For the original PVOL-FC-chunk where no swap
destination chunk exists, the failure swap program 305 overwrites the
content (LU# and chunk #) of the original SVOL-FC-chunk on the content of
the original PVOL-FC-chunk, and deletes the content of that original
SVOL-FC-chunk (S68). If failure occurs to the original PVOL by this
processing, the original SVOL-chunk is switched to the new PVOL-chunk if
the original SVOL-chunk corresponding to the original PVOL-FC-chunk is an
FC-chunk. And if the original SVOL-chunk corresponding to the original
PVOL-chunk is an SATA-chunk, then an FC-chunk selected from the plurality
of pool chunks is corresponded to that SATA-chunk, and the selected
FC-chunk is switched to the new PVOL-chunk. As a result, each of the
plurality of original PVOL-chunks registered in the left column (original
data column) of the failure handling volume copy management table 306 is
switched to the original SVOL-FC-chunk or the above mentioned selected
FC-chunk, and a new PVOL comprised of the original SVOL-FC-chunk and the
above mentioned selected FC chunk are generated. FIG. 13 (A) shows the
status of the failure handling volume copy management table 306 before
update, and FIG. 13 (B) shows the status of the table 306 after update.

[0154] By this update processing in S68, the plurality of FC-chunks out of
the original SVOL-chunks are all switched to new PVOL-FC-chunks, so new
SVOL-chunks for this amount of chunks are required. So the failure swap
program 305 selects the required number of FC-chunks from the plurality
of pool chunks, and registers the selected FC-chunks in the middle column
of the failure handling volume copy management table 306 and the volume
copy management table 308 as new SVOL-chunks. And the failure swap
program 305 copies the data in the FC-chunks, which were original
SVOL-chunks, to the new SVOL-chunks (S69).

[0155] Then the failure swap program 305 writes the write data saved in
S63 to the new PVOL. The failure swap program 305 provides the
information on the new PVOL (e.g. external LU number and storage
capacity) to the host device 100 when a predetermined inquiry command
(e.g. inquiry command based on SCSI protocol) from the host device 100
(S69). By this, the host device 100 can recognize the new PVOL.

[0156] The above is the processing flow executed by the failure swap
program 305. In the processing in S68, the failure swap program 305 may
update the content of the volume copy management table 308 in the same
way. The content of the original SVOL-chunk switched to the new
PVOL-chunk may be deleted from the failure handling volume copy
management table 306 and volume copy management table 308.

[0157] According to the above mentioned embodiment, each of the plurality
of LUs existing on the storage control system 200 is divided into a
plurality of chunks. The PVOL is comprised of only FC-chunks, but an SVOL
is comprised of both FC-chunks and SATA-chunks. And to each of the
plurality of SVOL-chunks, either an FC-chunk or SATA-chunk selected from
the plurality of pool chunks is dynamically corresponded. The type of
corresponded chunk is switched depending on the status of data write to
the PVOL. Specifically, to the SVOL-SATA-chunk corresponding to the
PVOL-FC-chunk with a high data update frequency, for example, an FC-chunk
existing on a high reliability high performance FC disk device is
corresponded, and to an SVOL-FC-chunk corresponding to a PVOL-FC-chunk
with a low data update frequency, a SATA-chunk existing on a low
reliability low performance but inexpensive SATA disk device is
corresponded. By this, the drop in speed of copy processing by a low
reliability low performance disk device and an increase in cost can both
be addressed.

[0158] According to the above mentioned embodiment, the storage capacity
ratio of an SVOL-FC in an SVOL (in other words the SVOL-SATA storage
capacity ratio) is automatically adjusted to be a preset disk ratio
threshold. Therefore the FC storage capacity ratio in an SVOL becomes the
ratio desired by the user, even if the user does not periodically perform
complicated settings.

[0159] According to the above mentioned embodiment, the storage capacity
ratio of an SVOL-FC is adjusted in the sequence of SVOL-chunks
corresponding to the PVOL-FC-chunks with a higher update frequency. By
this, the storage capacity ratio of an FC is efficiently adjusted.

[0160] According to the above mentioned embodiment, when a failure occurs
to the original PVOL, even if the chunk corresponded to the original
PVOL-chunk is an SATA-chunk, the data in the SATA-chunk is shifted to the
FC-chunk selected from the plurality of pool chunks, and the FC-chunk is
switched to the new PVOL-chunk. By this, the new PVOL-chunk constituting
the new PVOL can be an FC-chunk regardless the type of chunk corresponded
to the original PVOL-chunk.

[0161] An embodiment of the present invention was described above, but
this is just an example in order to describe the present invention, and
it is not intended to limit the scope of the present invention to only
this embodiment. The present invention can be implemented by various
other embodiments. For example, the above embodiment can be applied to a
storage device with an attribute level other than reliability or
performance. The above embodiment can be applied even when a plurality of
LUs are distributed in two or more devices (e.g. a PVOL exists in a
storage control system 200 and an SVOL exists in another storage control
system). Also in the above embodiment, there are two levels of disk
devices, one has high reliability and high performance, and the other has
low reliability and low performance, but more levels of disk devices may
be used. Also in the present embodiment, a plurality of thresholds may be
used for at least one of the update frequency threshold and the disk
ratio threshold, for a more refined adjustment. Two types of disk ratio
thresholds may be provided for the FC storage capacity ratio and the SATA
storage capacity ratio. The data update frequency is a number of times of
data updates in a predetermined period, but may simply be an update
frequency, regardless the period.